To assess the correlates of supraventricular arrhythmia (SA) in the late hospital phase of acute Q-wave myocardial infarction (MI), continuous 24-h ambulatory electrocardiographic monitoring, gated cardiac pool scan, modified exercise test, and chest x-ray were reviewed in 102 patients. Supraventricular tachyarrhythmias were seen in 11 patients, atrial premature beats in 42 patients; 49 patients did not have SA. Multiple discriminant analysis was used to determine the important variables contributing to the occurrence of SA. Variable included age, sex, history of previous MI, hypertension, location of MI, moist rales at time of admission, cardiothoracic ratio, ejection fraction, wall motion abnormality, exercise test result, duration of exercise and use of digitalis. Moist rales, digitalis, age and cardiothoracic ratio were the predictors of SA. Aging, hemodynamic change imposed on the left ventricle, and arrhythmic effects of digitalis are the major factors associated with SA in the late hospital phase of acute MI.